An important aspect of the preparation of textiles from cellulosic fibers is the removal of non-cellulosic components found in the native fiber, as well as the removal of impurities, such as compounds added to the fiber as sizing and lubricants used in the processing machinery. The removal of non-cellulosic impurities, termed "scouring", optimally results in a fabric with a high and even wettability that, consequently, can be evenly bleached and/or dyed.
Conventional scouring processes typically utilize highly alkaline chemical treatment, which results not only in removal of impurities but also in weakening of the underlying cellulose component of the fiber or fabric. Furthermore, chemical scouring creates environmental problems in effluent disposal, due to the chemicals employed and the materials extracted from the fibers. Consequently, there is a need in the art for scouring methods that are specifically targeted to removal of impurities and that are environmentally friendly.
Enzymatic scouring of textiles has been performed using multicomponent fungal enzyme systems comprising pectinases and cellulases that are active at a pH of about 4-5 (Bach et al., Textilveredlung 27:2, 1992; Bach et al., Textilpraxis International, March 1993, p. 220-225; Rossner, Melliand Textilberichte 2:144,1993; Rossner, Textilveredlung 30:82,1995; Hardin et al., 1997 Proceedings Beltwide Cotton Conferences, pp. 745-747; Li et al., Textile Chemist and Colorist 29:71, 1997; Li et al., 1997 International Conference & Exhibition (AATCC), pp. 444-454). In these studies, only a small proportion of the total enzyme activity in the preparations is useful for scouring. These methods thus require the use of large amounts of the enzyme preparation, making them economically unfeasible. Bacterial pectinases, sometimes combined with hemicellulases such as arabinanase, have also been used; these enzymes are typically active at higher pHs (International Patent Application WO9802531; Sakai et al., Textile Engineering (in Japanese), 45:301, 1992; Japanese patent 6220772; Sakai, Dyeing Industry (in Japanese) 43:162, 1995). All reported bacterial pectinases, however, require divalent cations for activity and are not generally active at temperatures over 60.degree. C. These properties limit their application to bioscouring of textiles, since (i) the textiles must be pre-boiled to attenuate the waxy cuticle overlaying the pectin layer and (ii) calcium ions tend to form insoluble salts which precipitate on the surface of the fibers.
Thus, there is a need in the art for bioscouring methods that can be performed in a single step, at temperatures near or above the melting temperature of the waxy cuticle of cotton (70.degree. C.) and in the absence of added divalent cations, using enzymes that effectively remove pectin and thereby facilitate the removal of pectin and other non-cellulosic impurities.